"Cries of censorship were heard this week at the University of Minnesota Duluth after a graduate art student’s exhibit at the Tweed Museum of Art was shut down for a day because of explicit content.
That came on the heels of controversy over a student art club’s display case and its use of a small nude mannequin some perceived as a child."

The topmost image is of a young Brooke Shields taken by Richard Prince. Next is a work by Mapplethorpe. Both are well-known and respected artists as well as accused child pornographers.

John Cooper, an English "leading criminal barrister" lays out some factors for deciding whether or not it's art or child porn:
"It's important to look at the circumstances surrounding the images. For instance: How old is the child? Have the photos been taken in vulnerable circumstances---in other words was there an element of exploitation involved?
...Another factor could be what kind of photographer took the pictures. If they are known to have a good reputation, then this will be relevant too."